Sonographic Diaphragm Dysfunction is an Unexpectedly Frequent Feature of Long COVID with Non-Specific Dyspnea and Fatigue (preprint)

ABSTRACT

Introduction/Aims The primary aim of this study is to define the sonographic diaphragm phenotype of Long COVID patients with non-specific dyspnea and fatigue. We analyzed patients referred from a pulmonary medicine COVID clinic without any intrinsic cardiopulmonary explanation for their new symptoms. Additionally, we report the functional outcomes of patients who completed an outpatient cardiopulmonary physical therapy program. Methods This was a retrospective cohort study (n = 37) of consecutive patients referred for neuromuscular assessment centered on B-mode ultrasound of the diaphragm muscle. Patients were recruited from a single academic hospital between February 25, 2021 and October 7, 2021. Results Sonographic abnormalities were identified in 65% (24/37) of patients, and in the vast majority of cases (23/24) was defined by low diaphragm muscle thickness. Thinner diaphragm muscles positively correlated with lower serum creatinine and creatine kinase values, but there was no association with markers of systemic inflammation. Eighteen patients participated in outpatient cardiopulmonary physical therapy that included respiratory muscle training, and 77.8% (n=14) had documented improvement. Discussion In the outpatient rehabilitation setting, patients with Long COVID frequently display low diaphragm muscle thickness, but intact muscle contractility on sonographic studies. We speculate this represents a form of disuse atrophy, which has a good response rate to cardiopulmonary physical therapy.